My Grandpa's hand saws, has to be over 100 years old

it is a mug abou 10cm by 10 cm and it is developing a blueish green substance but only a bit of it

Description:
I’m submitting several original Charga-Plates for appraisal, including one from the iconicJohn Wanamaker Department Store with its original red leather case. Most are in good condition, showing typical signs of age with minor surface wear but clear embossing and intact structure. These appear to be mid-20th-century pieces, possibly from the 1940s–1950s, and were likely issued to store customers as early credit identification.

Of particular interest is the Wanamaker Charga-Plate, which has historical relevance given the brand’s presence in Philadelphia and New York. The remaining plates also include variations in design and issue location, and I’m curious whether any are considered rare or carry added value based on their merchant origin.

I’d appreciate insights on:
- Estimated current market value
- Rarity and collectibility
- Historical context

Let me know if close-up photos will help